The invention concerns a method for assembling a structure that is formed from several modules that are disposed on top of each other, such as a wind power plant or the like, wherein a first module of the structure is initially erected and at least one further structural module is subsequently disposed onto the first structural module or the previously erected structural modules by lifting at least the at least one further structural module to the level of its assembly position by means of a lifting gondola in such a fashion that contact between the lifting gondola and the previously erected structural module(s) is prevented at least during movement of the lifting gondola. The invention also concerns a device, which is suited for performing such a method, for assembling a structure that is formed from several modules that are disposed on top of each other, such as a wind power plant or the like, with a lifting gondola that can be moved between a first position in which it can receive a structural module to be assembled, and a second position at the level of the assembly position of the structural module to be mounted on a previously erected structural module, wherein the lifting gondola is guided in such a fashion that contact between the lifting gondola and the previously erected structural module(s) is prevented at least during movement of the lifting gondola along the auxiliary mast.
There are many different conventional modular structures of the above-mentioned type, in particular, in the form of wind power plants and also in the form of TV/radio towers, bridges—or to be more precise: bridge piers, etc. In particular, wind power plants are becoming more and more important in view of decreasing fossil fuels. Consequently, their sizes and efficiency increase and the locations where they are erected should provide continuous wind power and be sparsely populated in order to be profitable and minimally affect the population. The increasing sizes and the fact that many locations are difficult to access, e.g. in particular at sea (so-called offshore plants), can cause considerable problems with respect to the assembly of such plants and also with respect to removal of the plant, if required. The same naturally also applies to structures of the above-mentioned type of similar size.
Wind power plants generally comprise a structure of several structural modules that are disposed on top of each other, which may be formed e.g. from welded steel tube, lattice girders or reinforced concrete elements. The ends of the structural modules may have corresponding mounting flanges for connection, which are generally provided on the inside of the hollow modules in order to facilitate access, e.g. via internal stairs or a ladder, for a technician who screws them in place, and also to provide an optically uniform overall impression. The structural modules themselves may either be cylindrical, in particular circular cylindrical, or conical, and taper towards the top. In both cases, the wall thickness may moreover decrease from module to module and/or within one module from the bottom to the top in order to reduce material. Modern wind power plants today have a height of up to approximately 120 m and an approximately equally sized rotor diameter, which obtains a power of up to approximately 5 MW. The length of the structural modules of such plants is often in a range of approximately 30 m, and having a structural module weight of approximately 150 t. The machine gondola, on which the rotor is disposed, may even have a weight of several 100 t.
In most cases, wind power plants of this type are presently assembled on site by means of cranes. In dependence on the location where the structural modules are erected, the structural modules are moved to their destination by means of special trucks or ships, where they are picked up by the assembly crane and lifted to their assembly position, whereby the assembly crane must hold them in position until they are completely fixed to each other, in particular, screwed and/or welded. For onshore assembly, extremely large mobile telescopic or lattice steel tower cranes are used, in which case the ground must be particularly levelled/compacted. For offshore assembly, special lifting ships are used, which have corresponding cranes and can be arranged at the sea bottom via supports that can be lowered such that the crane is arranged in a stationary fashion independently of the state of the sea.
It is obvious that the use of such cranes requires a considerable amount of time and cost, which includes the transport of the crane to and away from the site and its erection, which may e.g. require the use of counterweights for erecting its arm. In addition thereto, strong winds or overall unfavorable weather conditions often naturally prevail at the site of erection, which not only applies for erection of such structures in the offshore region. It may happen that the time for erecting a plant at a location that is favorable for operating a powerful wind power plant is actually limited to only a few months of the year due to the assembly preconditions. In contrast thereto, it usually takes some weeks to erect the plant, which may be considerably extended by unfavorable weather conditions requiring stoppage of any work. Finally, there is only a limited number world-wide of lifting devices for such wind power plants of continuously increasing size.
DE 103 08 239 A1 describes a method and a device for erecting a wind power plant that is formed from several structural modules that are disposed on top of each other, the top structural module of which bears the machine gondola with the rotor. The plant is erected by lifting each previously erected structural module to such an extent that the following structural module can be inserted below the lower one of the previously erected modules and can be fastened thereto. In consequence thereof, the previously finished overall structure must always be lifted to a suitable height in order to add further structural modules. The machine gondola of the wind power plant is thereby mounted to the initially erected structural module, in the present case, the upper module, already at the start with the consequence that it must always be lifted as well. The lifting means that is used for this purpose has corresponding complex dimensions and comprises linear guidances having the length of one respective structural module, which must also accept the wind forces that act during assembly. The most important disadvantage, however, is that also in this case, a crane is obligatory at least for disposing the machine gondola onto the first (upper) structural module, which entails the above-described problems.
EP 1 057 770 B1 discloses a method and a device of this type that are, in particular, also suited to erect an offshore wind power plant. Sections of a guiding rail are welded to each individual mast module of the wind power plant such that a lifting gondola that is driven along previously erected mast modules by means of a cable is guided on the guiding rails, thereby preventing contact between the lifting gondola and the mast to largely prevent damage thereof and also, in particular, of an anti-corrosion paint. Disadvantageously, considerable transverse forces and bending moments act on the guiding rails that are rigidly connected to the mast modules, during movement of the lifting gondola, which necessitates extremely expensive over-dimensioning of the mast modules, in particular, for relatively large masts that are required for offshore wind power plants in order to accept the additional stress that is generated during erection. The guiding rails themselves that are only used to erect the mast also produce considerable additional cost. It also takes a relatively great amount of time to erect such a mast since the mast modules that are transported on the lifting gondola in an upward direction along the guiding rails must initially be oriented with respect to the previously erected mast modules, and the mast module must then be screwed to the upper previously erected module prior to moving the lifting gondola again along the guiding rail of the last erected (upper) mast module.
It is the underlying purpose of the invention to further develop a method and a device of the above-mentioned type by means of a simple and inexpensive construction such that the above-mentioned disadvantages are at least largely eliminated.